A valve-lifter may be mentioned as an example of products which need a process for cutting the outside surface of the blank and making said outside surface concentric with a concave spherical seat in the inside of its bottom.
To avoid the need for machining the concave spherical internal seat, this seat is formed, in accordance with the invention, by casting, or forging. To cast the seat, a steel ball is provided at the end of the core in a mold in which the hollow cylindrical valve lifter body blank is cast. Where the seat is forged, and forging can be hot or cold forging, and the seat is formed by a forging punch with a spherical tip. After the rough body blank is formed its exterior surface is correctively cut to make this exterior surface concentric with the internal spherical seat.
In accordance with this invention the rough blank, with its concave internal seal formed during casting, or by forging, is mounted on a unique holder which centers the blank with respect to the axis of the concave seat and permits reliable corrective cutting of its outside surface concentric with the seat. The technique of the invention simplifies forming the cylindrical body by eliminating the need for machining the concave seat.